Question
Why do I need to repeat a 28-day negative HIV test at three months?
16 September 2023. Related: All topics, HIV testing.
I don’t understand how if a 28 day Duo test when negative is conclusive, why does the information on i-Base say …
“As with antibody tests, a small percentage of people may have a delayed response to HIV so people using this test four weeks after any potential exposure are routinely recommended to confirm a negative result three months later.”
I was negative at 35 days and was moving on with my life until I read this,
please help.
Answer
Note: Since 2021, UK guidelines recommend that a negative result at six weeks using a 4th generation HIV Ag/Ab test does NOT need to be confirmed with a second test. Testing earlier than 6 weeks still needs a second test to confirm a negative result. The earlier answer is kept online to explain the complications of HIV teting. See https://i-base.info/qa/11844
……………
UK recommendations have changed several times on this question. In 2010 when this question was first posted, UK guidelines routinely recommended retesting so the i-Base information referenced this.
Since 2014, the guidelines change to only recommend retesting if this was linked to a high risk of HIV. (See statement below).
Updated guidelines also recommend not having to wait for 28 days before testing. Instead, it is better to test as soon as possible and then retest 4 weeks later. This change was important. It stops people worrying and might pick up early infections. Unfortunately, we still hear of clinics ask people to wait 4 weeks (or longer) before testing.
Even with tests that are incredibly accurate, health care workers have a duty to explain the best chance for a confirmed negative status. The reason for recommending the confirmatory test is two-fold:
- A small number of people have individual responses to HIV that may not be picked up by the test at 28 days. When the tests are approved, this is based on a panel of responses from an extensive store of timed blood samples. These show that some samples pick up a positive test result after only a week and some after more than a month, but that most are positive for the p-24 antigen at around 15 days. Some people may not produce enough p-24 antigen for the test to pick this up though, so together with the antibody response, the combined test are still more than 95% accurate at four weeks.
- The second reason relates to the possibility that someone who is not picked up, might put another person at risk of HIV. This duty of care should be explained when you take the test the test and are given the results. So although you have almost certainly not caught HIV, you should use condoms with sexual partners, until the confirmatory result.
I wish there was an accurate test at two weeks or one day, but there isn’t. The technology is more complicated than most people realise, and the concern for future transmission of HIV, however slight the possibility, is a professional health care concern.
Please don’t let this cause you stress, you are almost certainly HIV-negative, but this is the detailed reason.
BASHH/EAGA Statement on HIV window period
November 2014
HIV testing using the latest (fourth generation) tests is recommended in the BHIVA / BASHH / BIS UK guidelines for HIV testing (2008). These test for HIV antibodies and p24 antigen simultaneously. A fourth generation HIV test on a venous blood sample performed in a laboratory will detect the great majority of individuals who have been infected with HIV at 4 weeks after specific exposure.
Patients attending for HIV testing who identify a specific risk occurring less than 4 weeks previously should not be made to wait before HIV testing as doing so may miss an opportunity to diagnose HIV infection (and in particular acute HIV infection during which a person is highly infectious). They should be offered a fourth generation laboratory HIV test and be advised to repeat it when 4 weeks have elapsed from the time of the last exposure.
A negative result on a fourth generation test performed at 4 weeks post-exposure is highly likely to exclude HIV infection. A further test at 8 weeks post-exposure need only be considered following an event assessed as carrying a high risk of infection.
Patients at ongoing risk of HIV infection should be advised to retest at regular intervals.
Patients should be advised to have tests for other sexually transmitted infections in line with advice on window periods for those infections (see BASHH guidelines at: www.bashh.org ).
Note: This answer was updated in January 2018 from an original post from October 2010. The additional note was added in September 2023.
Dear Charlie,
Kindly respond. My life has been a living hell for the past two months. I have also been intimate with my wife as explained above. The symptoms which my wife and myself are experiencing have recently put my life through big turmoil and we don’t even sleep sometimes at night. PLEASE, PLEASE DO HELP ME AND MY FAMILY FROM THIS TORTURE. It’s really my neck pain and dizziness as far as my symptoms are concerned and as far as my wife’s symptoms goes its really the weight loss and recent vaginal problems she experienced is making her sick. Please respond Charlie !!!
Regards,
VJ
Dear VJ,
I am not sure there is anything else I can say to help you. I am not a doctor but a HIV treatment advocate. I can only give information on matters regarding HIV and you do not have HIV. You need to go and see your doctor so they can diagnose what is wrong with you.
Best wishes
Charlie
Dear Charlie,
I got myself tested once again in Dec using the ECLIA P24 and ANTIGEN tests and it came out negative. That’s 9th week post exposure. You told me that further testing not required but I couldn’t stop my fears and so got tested once again which was negative. Today I have experienced some more black spots on my left side of my face, firstly they appeared on my fore head and now left side of my cheeks with mild itching, kindly help, what are these?
The dizziness still persists where as the throat soreness has totally gone. I am very afraid. More over I would like to add that when I was diagnosed with diabetes I lost around 6kgs of weight but in these two months I have gained around 3kgs but am still around 3-4kgs less in weight compared to three months ago. My wife too has recently lost around 4-5kgs in weight that is also unexplained. She is not experiencing anything else expect occasional mild nausea and some small red spots in the upper back. She had also experienced a vaginal problem a few days ago but after taking the doctor’s advice and medicines that has gone. Is this related to some thing? I am very very afraid. Please experts please advice. Waiting anxiously. Please, please I’ll be highly obliged if I am answered. It’s not only about my life but my wife as well. Please
Regards,
VJ
For information about when a test is accurate please follow this link.
Hi,
I would appreciate your response to my question.
I had unprotected sex with prostitute in October 2010. The lady told me she never had unprotected sex before me with anybody. After 42 days i.e on the 43rd day HIV test was negative should I test again? Please help.
I am sorry to hear of your recent diagnosis. The different test results could have occurred for several reasons, firstly it could be that your original negative test was a false negative, it could be that you have very recently become infected or it could be that you are one of the extremely rare people who take a lot longer to generate antibodies to HIV. Either way you need to focus you energy on the future and your health now. For all the information you will need regarding HIV treatment please follow this link to the ‘Introduction to Combination Therapy‘ guidebook
I was negative after three months but after 5 months my test was positive and is not a false positive result
It is possible that you have had a false positive result which is where the result comes out positive when it is really negative. This is rare but does happen sometimes. For more information please follow this link and scroll down until you reach the section about ‘false positives’. You need to go and have a confirmatory test to see whether or not you have HIV.
I got tested 6 months from my last exposure and it was negative and then I tested again 14 months later. Now my result is positive but since the last exposure I never put myself a risk again why has this happened?
We are not doctors but HIV treatment advocates and so I cannot comment on the medications the doctor has given you or say what I think is causing these symptoms. However, if you have had several negative HIV tests then you do not have HIV. Something else must be causing these symptoms and you should discuss this with your doctor.